I just got a Yamaha Silent Brass mute, and noticed something it does... something very similar to my wah-wah mute... it's very sensitive to my tongue position, the shape and, I guess, natural resonance of the cavity of my mouth. So when I'm doing tongue stops, the trumpet will also start going "wah wah wah wah." It's pretty annoying... is this normal for everyone? Is there a way to prevent it? Is my technique wrong? I'm touching the tip of my tongue to the hard ridge behind my top teeth.